3D Time-of-flight distance measurement with custom - Universität ...

DEMODULATION PIXELS IN CMOS/CCD 141
Resulting distance accuracy in cm
25
20
15
10
5
0
No average
Average: 16
0 2000 4000 6000 8000 10000
Optical power in fW per pixel
Figure 5.24 Measured distance accuracy versus the received optical power per
pixel.
Table 5.3 transforms the optical power per pixel into the equivalent number of
electrons integrated totally and integrated per modulation period. We see that we
still get a distance resolution of 4 cm if only one electron is generated, statistically
speaking, every 13 th modulation period. Since the sampling interval is only half the
modulation period, this means that one electron will be integrated to the sampling
point only every 26 th modulation period for this range resolution. For generation of a
photoelectron every 4 th modulation cycle, the range accuracy is 1.6 cm, i.e. a time
resolution of 100 picoseconds or a phase resolution of 0.75 degrees. In [SP4] a
phase resolution of 0.9 degrees has been reported for an 8-tap demodulation pixel
operated at 8kHz modulation frequency, i.e. more than 3 orders of magnitude
slower.
In Section 5.2.8 we compare these measured results with the theory introduced in
Section 4.2.